Method and apparatus for producing product from stock pulp sheet

ABSTRACT

A method of production of a product from a stock pulp sheet uses conveyor rolls to convey a stock pulp sheet to a crusher. During conveyance to the crusher, a defective part in the stock pulp sheet is detected by a detector. The detected defective part is removed from the stock pulp sheet by a remover. The stock pulp sheet from which the defective part is removed is supplied to the crusher to produce crushed pulp. The produced crushed pulp is used to produce a product in a product producer.

TECHNICAL FIELD

The present invention relates to a method and apparatus for producing aproduct from a stock pulp sheet.

BACKGROUND ART

In the past, the method has been known of crushing a stock pulp sheet bya crusher to produce crushed pulp, forming component parts such as anonwoven fabric or absorbent mat from the produced crushed pulp, andassembling these component parts to produce a product such as adisposable diaper or sanitary napkin.

In this regard, a stock pulp sheet sometimes includes a defective partwhere for example a piece of bark or other foreign matter is mixed in orchanges color. If such a defective part for example remains at thesurface in contact with the skin such as the top sheet, the commercialvalue of the product will end up falling.

Therefore, a defective product rejection system which detects adefective part present in a product and rejects a product containing thedefective part as a defective product is known (see PLT 1).

CITATION LIST Patent Literature

PLT 1: Japanese Unexamined Patent Publication No. 2002-79187

SUMMARY OF INVENTION Technical Problem

A defective product rejected as explained above is generally discarded.However, it is uneconomical to discard an entire product if thedefective part is just minor.

In this regard, if detecting and removing the defective part at thestage of the stock pulp sheet, this problem could be resolved. In thisregard, a stock pulp sheet is conveyed toward a crusher at aconsiderably fast speed. Further, a defective part is sometimes presentnot at the surface of the stock pulp sheet, but inside it, and the basisweight of a stock pulp sheet is considerably high. For this reason, atthe present time it is considered difficult to reliably detect andremove a defective part in a stock pulp sheet and, at the product stage,the defective part is detected and the entire product is discarded. Iftemporarily stopping the conveyance of a stock pulp sheet to thecrusher, it would be possible to reliably detect and remove a defectivepart, but if doing this, the productivity of the product may be liableto remarkably drop.

Solution to Problem

According to one aspect of the present invention, there is provided amethod of producing a product from a stock pulp sheet, comprising thesteps of:

conveying the stock pulp sheet to a crusher,

detecting a defective part in the stock pulp sheet by a detector duringthe conveyance to the crusher and removing the detected defective partfrom the stock pulp sheet by a remover,

feeding the stock pulp sheet from which the defective part has beenremoved into the crusher to produce crushed pulp, and

using the produced crushed pulp to produce a product.

According to another aspect of the present invention, there is providedan apparatus for producing a product from a stock pulp sheet, comprising

a crusher which crushes the stock pulp sheet to produce crushed pulp,

a conveyor which conveys the stock pulp sheet toward the crusher,

a detector which detects a defective part in the stock pulp sheetsduring conveyance to the crusher,

a remover which removes from the stock pulp sheet the detected defectivepart detected during conveyance to the crusher, and

a producer which uses the produced crushed pulp to produce a product.

Advantageous Effects of Invention

It is possible to produce a product with a high economy and productivitywhile reliably detecting and removing a defective part.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overview of a production apparatus;

FIG. 2 is a partial front view of a hole saw;

FIG. 3 is a schematic perspective view of a mover;

FIG. 4A is a view explaining the action of removal of a defective part;

FIG. 4B is a plan view of a circular region;

FIG. 5 is a view of another example of a production apparatus; and

FIG. 6 is a view of still another example of a production apparatus.

DESCRIPTION OF EMBODIMENTS

FIG. 1 shows an apparatus 1 for producing a product from a stock pulpsheet. Here, the stock pulp sheet is produced by shaping pulp made fromwood, a nonwood material, recycled paper, synthetic fibers, etc. into asheet and drying the result.

In the production apparatus 1 shown in FIG. 1, the stock pulp sheet isprepared in the form of a roll 2. The stock pulp sheet 3 unwound fromthe roll 2 is guided by a plurality of guide rolls 4 and conveyed by apair of conveyor rolls 5 to a crusher 6.

Upstream of the crusher 6, that is, between the roll 2 and the crusher6, a detector 10 is provided for detecting a defective part in the stockpulp sheet 3. The detector 10 is provided with a light source 11arranged at one side of the stock pulp sheet 3 and a camera 12 arrangedat the other side of the stock pulp sheet 3. The light source 11 emitslight to the stock pulp sheet 3. The transmitted light obtained at theother side of the stock pulp sheet 3 at that time is obtained by thecamera 12. Note that, it is also possible to provide a plurality ofcameras 12 arranged in a width direction of the stock pulp sheet 3.

Further, downstream of the detector 10, that is, between the detector 10and the crusher 6, a remover 20 is provided for removing a defectivepart detected by the detector 10 from the stock pulp sheet 3. Theremover 20 is provided with a cutout device 21 provided at one side ofthe stock pulp sheet 3 for cutting out a defective part from the stockpulp sheet 3, a mover 22 for making the cutout device 21 move in the x-,y-, and z-directions, a pickup device 23 provided at the other side ofthe stock pulp sheet 3 for picking up a defective part cut out from thestock pulp sheet 3, and a distance detector 24 for detecting aconveyance distance of the stock pulp sheet 3. Note that, x, y, and zindicate the conveyance direction, width direction, and thicknessdirection of the stock pulp sheet 3 around the remover 20, respectively.In the example shown in FIG. 1, the x-and y-directions are substantiallyhorizontal and the z-direction is substantially vertical.

The cutout device 21 is provided with a rotary blade and a drive devicefor driving rotation of the rotary blade. This rotary blade is forexample comprised of a hole saw 21 h such as shown in FIG. 2. Thediameter of the hole saw 21 h is set in accordance with the size of thedefective part to be removed. Note that, the rotary blade can also becomprised of a compass type rotary cutter.

The mover 22, as shown in FIG. 3, is provided with an x-direction mover22 x extending in the x-direction, a y-direction mover 22 y extending inthe y-direction, and a z-direction mover 22 z extending in thez-direction. The x-direction mover 22 x carries the y-direction mover 22y and makes it move in the x-direction, the y-direction mover 22 ycarries the z-direction mover 22 z and makes it move in the y-direction,and the z-direction mover 22 z carries the cutout device 21 and makes itmove in the z-direction. In this way, the cutout device 21 or hole saw21 h can move in three dimensions.

The pickup device 23 is for example connected to the y-direction mover22 y. Therefore, it can move together with the cutout device 21 in thex-direction. At the top surface of the pickup device 23 positionedapproximately right under the hole saw 21 h, a suction slit 23 s isformed. This suction slit 23 s is given a negative pressure. That is, inthe example shown in FIG. 1, the pickup device 23 picks up the removeddetective part by a suction action.

Further, flat areas 23 f are formed at the upstream side and downstreamside of the suction slit 23 s at the top surface of the pickup device23. The stock pulp sheet 3 is moved over these flat areas 23 f andtherefore conveyed while being supported by these flat areas 23 f.

Referring again to FIG. 1, the distance detector 24 is provided with arotary encoder for example built into the conveyor rollers 5. The rotaryencoder 24 generates an output pulse corresponding to the amount ofrotation of the conveyor rollers 5. The amount of rotation of theconveyor rollers 5 expresses the distance of conveyance of the stockpulp sheet 3 and the distance of movement of a defective part.

The outputs of the camera 12 and rotary encoder 24 are input to theinput side of a computer 30. The output side of the computer 30 isconnected to the cutout device 21 and mover 22.

The computer 30 detects a defective part in the stock pulp sheet 3 basedon the transmitted light obtained by the camera 12. That is, it comparesthe intensity of the transmitted light obtained by the camera 12 with apredetermined threshold value, judges a part with an intensity of thetransmitted light smaller than the threshold value as a defective part,and judges other parts as not defective parts. By doing this, it ispossible to simultaneously and easily detect defective parts which canexist at the two surfaces and inside of the stock pulp sheet 3.

Note that the white pieces of pulp which can be included in a stock pulpsheet 3 and regions with remarkably uneven basis weight can be detectedusing the above detector 10.

When a defective part in the stock pulp sheet 3 is detected, the holesaw 21 h is made to move by the mover 22 to the defective part. In thiscase, the x-direction position and y-direction position of the defectivepart are identified from the output of the rotary encoder 24 and theoutput of the camera 12.

Next, the hole saw 21 h is driven to rotate while being made to descendin the z-direction. As a result, as shown in FIGS. 4A and 4B, a circularregion C including the defective part D is cut out from the stock pulpsheet 3 by the hole saw 21 h. The cut out circular region C is suckedinto the suction slit 23 s.

In this case, the hole saw 21 h is made to move in synchronization withthe conveyed stock pulp sheet 3, in particular the defective part D,while removing the defective part D. That is, during removal of thedefective part D, the hole saw 21 h is made to move at substantially thesame speed as the defective part D in the x-direction or the conveyancedirection. As a result, the defective part D is removed without stoppingthe stock pulp sheet 3 and in particular without slowing the stock pulpsheet 3. Therefore, the detection and removal of a defective part do notcause the processing ability of the stock pulp sheet 3 to drop.

Further, the pickup device 23 is also moved synchronously with thedefective part D. As a result, as shown in FIG. 4A, when the hole saw 21h cuts out the defective part D or circular region C, the stock pulpsheet 3 around the defective part D is supported by the flat areas 23 fof the pickup device 23. Therefore, it becomes possible to stably andeasily cut out the defective part D or circular region C.

When the defective part D is removed, the hole saw 21 h is raised toseparate it from the stock pulp sheet 3 and then returned to its initialposition.

Referring again to FIG. 1, the stock pulp sheet from which the defectivepart D has been removed is next fed to the crusher 6. In the exampleshown in FIG. 1, the crusher 6 is provided with a hammer mill. Thecrusher 6 crushes the stock pulp sheet 2 by the hammer mill and producescrushed pulp or fluff pulp. The crushed pulp is next conveyed by aconveyor fan 7 to a product producer 8.

The product producer 8 uses the crushed pulp to produce a product. Here,the product includes a nonwoven fabric used for wipes, cleaning sheets,etc., absorbent articles such as sanitary napkins and disposablediapers, paper, etc. When the product is an absorbent article, thecomponent elements of the absorbent article such as the fluff pulp matis also produced by the product producer 8.

In this case, since the defective part is removed from the stock pulpsheet 3, the crushed pulp contains almost no defective parts. Therefore,the product also contains almost no defective parts. As a result, thereare almost no more products which are discarded due to the inclusion ofa defective part, so the manufacturing costs of the present invention isgreatly lowered.

Further, when directly producing a fluff pulp mat from crushed pulpproduced using a hammer mill, making the basis weight of the fluff pulpmat uniform requires the continuous supply of stock pulp sheet 3 to thecrusher 6. In the embodiment according to the present invention, thestock pulp sheet 3 can be supplied to the crusher 6 without the sheetbeing stopped, so the basis weight of the fluff pulp mat can be madeuniform.

In the embodiments of the present invention discussed up to here, thestock pulp sheet 3 is fed to the crusher 6 in the form of a continuousweb unwound from a roll 2. However, as shown in FIG. 5, it is alsopossible to prepare a stack 2 a of separate square-shaped stock pulpsheets 3 a and successively feed the stock pulp sheets 3 a from thestack 2 a by a conveyor belt 5 a. In this case, the conveyor belt 5 aconveys the stock pulp sheets 3 a with two side edges gripped. Further,a rotary encoder 24 is incorporated in a roller of the conveyor belt 5a.

Note that, in the example shown in FIG. 5, the stock pulp sheets 5 a areconveyed separated from each other. In this case, by providing areservoir which temporarily stores the crushed pulp between the crusher6 and the product producer 8, it is possible to give a fluff pulp mat auniform basis weight. However, with the direct connection system notusing a reservoir, it is also possible to have the rear end of apreceding stock pulp sheet 5 a and the front end of a succeeding stockpulp sheet 5 a be contiguous.

Alternatively, when producing a nonwoven fabric or paper, as shown inFIG. 6, the crusher 6 may also be provided with a pulper 6 a. In thiscase, the crushed pump produced by the pulper 6 a is fed to the productproducer 8 in the form of a slurry.

Further, as shown in FIG. 6, it is also possible to provide a scrapremover 25 which uses for example a suction action to remove the scrapsproduced when the cutout device 21 cuts out a defective part. This scrapremover 25 may for example be fastened to the cutout device 21 andtherefore move together with the cutout device 21.

Furthermore, in the embodiments of the present invention discussed up tohere, one detector 10 and one remover 20 each were provided. However, aplurality of detectors 10 and removers 20 may also be provided. If doingthis, it is possible to reliably detect and remove a defective part.

When providing a plurality of detectors 10, these detectors 10 may forexample be arranged serially in the direction of conveyance of the stockpulp sheet 3. Further, it is also possible to have a certain detector 10emit light from one side of the stock pulp sheet 10 and receive thetransmitted light at the other side and have another detector 10 emitlight from the other side of the stock pulp sheet 10 and receive thetransmitted light at the one side. Alternatively, it is also possible tomake the light intensity of the light source 11 or the dimensions of thedefective part to be detected different for each detector 10. Whateverthe case, if doing this, it is possible to more reliably detect adefective part.

Furthermore, in the embodiments of the present invention discussed up tohere, the remover 20 was provided with a hole saw 21 h to cut out thedefective part from the stock pulp sheet. However, the remover 20 mayalso be provided with a die cutter to punch out the defective part fromthe stock pulp sheet. However, the basis weight of the stock pulp sheetis for example 680 g/m² or considerably high, so to reliably punch out adefective part, the remover 20 becomes considerably heavy. For thisreason, making the remover 20 move in synchronization with the defectivepart becomes difficult. As opposed to this, with the hole saw 21 h, sucha problem does not arise.

Note that, the embodiments explained up to here can also be combinedwith each other. That is, for example, in the example of FIG. 1 or FIG.2, the scrap remover 25 can also be provided.

REFERENCE SIGNS LIST

1 apparatus

3 stock pulp sheet

5 conveyor roll

6 crusher

8 product producer

10 detector

20 remover

1. A method of producing a product from a stock pulp sheet, comprising the steps of: conveying the stock pulp sheet to a crusher, detecting a defective part in the stock pulp sheet by a detector during the conveyance to the crusher and removing the detected defective part from the stock pulp sheet by a remover, feeding the stock pulp sheet from which the defective part has been removed into the crusher to produce crushed pulp, and using the produced crushed pulp to produce a product.
 2. A method as set forth in claim 1, wherein said remover is provided with a rotary blade and said rotary blade cuts out a circular region including said defective part from the stock pulp sheet to remove the defective part from the stock pulp sheet.
 3. A method as set forth in claim 1, which makes said remover move in synchronization with the conveyed stock pulp sheet while using the remover to remove said defective part.
 4. A method as set forth in claim 1, which detects said defective part based on a transmitted image obtained at another side of the stock pulp sheet when emitting light from one side of the stock pulp sheet.
 5. A method as set forth in claim 1, wherein said product is one product selected from a nonwoven fabric, absorbent article, and paper.
 6. An apparatus for producing a product from a stock pulp sheet, comprising a crusher which crushes the stock pulp sheet to produce crushed pulp, a conveyor which conveys the stock pulp sheet toward the crusher, a detector which detects a defective part in the stock pulp sheets during conveyance to the crusher, a remover which removes from the stock pulp sheet the detected defective part detected during conveyance to the crusher, and a producer which uses the produced crushed pulp to produce a product. 